endurance dizziness

Why is dizziness or light-headedness such a relatively common phenomenon in endurance sports? And why does it seem more likely to occur at the finish line, rather than out on the course?

Years ago, the conventional wisdom was that dehydration was the primary cause of collapse at the end of long endurance races. Although fluid and electrolyte loss might well be a contributing factor to what’s going on, it has been surmised that something called ‘Exercise Associated Postural Hypotension’ (EAPH) is far more likely to be to blame in the vast majority of cases.

To better understand what EAPH is (and why it happens) it’s useful to appreciate some of the basics around how blood flow and blood pressure are regulated during exercise.

Source: Is Dehydration Making You Feel Dizzy? – TrainingPeaks